Needling machines are generally known and are described in, for example, “Vliesstoffe” (“Nonwovens”), by Lünenschloβ and Albrecht, Georg-Thieme-Verlag, Stuttgart, 1982, pp. 122-129.
The needle boards used in a needling machine of this type usually consist of a base plate of aluminum with bores, from which the needles project, and a plastic plate, made especially of polyamide (Nylon), which is attached to the back of the base plate and which is provided with a corresponding set of bores. Grooves, to which the bores lead, are milled into the back of the plastic plate. The grooves serve to accept the bent-over sections of the needles shafts located at the tear of the needles. The bores in a needle board of this type are closely matched to the diameters of the shafts of the needles held in the needle board, so that the needles are seated as firmly as possible in the needle board and do not wobble during use. The back of the needle board lies on the needle bar of the needling machine, to which it is attached, as a result of which the bent-over sections of the needles are held in the grooves.
Because the service life of needles is limited, they must be replaced from time to time. The process of inserting the needles into the needle board and of removing them from the board again, however, has the effect of wearing down the bores and thus of loosening the fit between the needle shaft and the bore in the aluminum base plate of the needle board to such an extent that eventually there is no longer enough clamping force present. The needles can therefore wobble in the bores and are bent out of shape during the needling process and can even break off.
Another disadvantage of these types of needle boards is that inserting the needles into the boards is a very tedious task, and thus the replacement of a needle board or the replacement of the needles in the needle board is always associated with a considerable amount of labor and with high cost.